1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to correcting quantized coefficients in a video codec, and more particularly, to correcting coefficients that are transformed from video data in the time domain to video data in the frequency domain, and are then quantized, by using a non-uniform statistical distribution of the quantized coefficients.
2. Description of the Related Art
According to video compression standards, such as Moving Picture Experts Group (MPEG) and H.26X, a transmission data stream is generally generated by compressing video data by sequentially performing a pre-processing operation, a transformation operation, a quantization operation, and an encoding operation on the video data.
In the transformation operation, various transformation methods are used for detecting a redundancy in video data in order to increase the efficiency of compression. In particular, a method of transforming video data in the spatial domain into coefficients in the frequency domain is often used. Representative examples of such a method are discrete cosine transformation (DCT) and wavelet transformation.
In the quantization operation, the values of the obtained coefficient are reduced to effective numbers of bits, which causes a loss of the original data. Since all lossy compression techniques include the quantization operation, the rate of data compression can be increased although the original data cannot be completely restored.
In video compression standards, such as Joint Photographic Experts Group (JPEG), MPEG, and H.26X, a non-uniform quantization technique is used. In the non-uniform quantization technique, additional coefficient correction values for respective coefficients that are transformed from video data according to any transformation method, such as DCT, and are then quantized are determined, and the quantized coefficients are corrected using the additional coefficient adjustment values. Conventionally, coefficient correction values for coefficients are measured in various ways and the coefficients are corrected by an encoder.